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本文试图对碱金属碱土金属元素的热稳定性和盐类的溶解性进行热力学分析。化合物的热稳定性可以运用热化学循环求得化合物分解反应的焓变ΔH~0 或自由焓变化ΔG~0,根据化合物分解产物的不同——单质或化合物,将它们分成两部份进行讨论。无水晶体盐类的溶解性可以应用标准溶解自由焓ΔG_s~0。进行判断,ΔG_s~0 可表示为:ΔG_s~0=ΔH_s~0-T(ΔS_s~0),或ΔG_s~0=ΔG_L~0+ΔG_h~0,这样溶解焓效应ΔH_s~0 和溶解熵效应ΔS_s~0 的大小应从升华和水化的相对大小作具体分析。应用热力学数据结合离子大小和电荷多少就可以方便地比较两类盐类溶解度大小。此外本文还应用标准自由焓近似公式不但说明盐类溶解性变化规律,并较好地说明同类中盐类溶解度最小的现象。
This article attempts to thermodynamically analyze the thermal stability of alkaline earth metal elements and the solubility of salts. Thermal Stability of Compounds The enthalpy change ΔH ~ 0 or the free enthalpy change ΔG ~ 0 of a compound decomposition reaction can be calculated by thermochemical cycle. They are divided into two parts according to the different elements or compounds of the compound decomposition products. The solubility of anhydrous crystalline salts can be applied to the standard solution of free enthalpy ΔG_s ~ 0. , ΔG_s ~ 0 can be expressed as ΔG_s ~ 0 = ΔH_s ~ 0-T (ΔS_s ~ 0) or ΔG_s ~ 0 = ΔG_L ~ 0 + ΔG_h ~ 0, thus the enthalpy effect ΔH_s ~ 0 and the dissolving entropy effect ΔS_s The size of ~ 0 should be specifically analyzed from the relative sizes of sublimation and hydration. Application of thermodynamic data combined with ion size and charge how much can easily compare the size of two types of salt solubility. In addition, this paper also uses the standard free enthalpy approximation formula not only shows the variation of salt solubility, and better explain the similar phenomenon of salt solubility.